Design Wind Power Turbine - Hybrid Anisotropic Materials for Wind Power Turbine Blades - page 33

bending.due.to.the.natural.variations.in.wind.speed..In.addition,.these.static.
and.fatigue.load.spectra.are.varied.during.rotation.
When.the.blade.points.upward.and.downward,.respectively,.this.is.caused.
by.the.natural.wind.shear,.which.is.the.increase.of.average.wind.speed.with.
increasing.height.over.the.terrain.
The.blades.are.also.exposed.to.gravity,.and.this.is.most.pronounced.when.
they.are.in.the.horizontal.position..These.loads.cause.bending.in.an.angle-
wise.mode,.and.a.given.blade.can.bend.one.way.on.the.right-hand.side.and.
the.opposite.way.on.the.left-hand.side.of.the.rotor.plane..This.explains.why.
the.edge-wise. bending.also.causes.fatigue.of.the.blade.material. and.struc-
ture.during.rotation..The.blades.are.exposed.to.centrifugal.forces.during.the.
rotation.of.the.rotor..During.the.limits.of.the.linear.blade.velocity,.the.rota-
tion.speed.is.relatively.low,.typically.from.20.rpm.to.10.rpm.for.large.blades..
Therefore,.the.longitudinal.tensile.loads.in.the.blades.are.relatively.low.and.
normally.are.not.taken.into.account.as.a.design.parameter..The.design.life-
time.of.modern.wind.turbines.is.normally.20.years,.and.the.corresponding.
number.of.rotations.is.in.the.order.of.10 8 .to.10 9 .

2.8.3 The Automatic 3-Axial Braiding Process

The. automation. VARTM. processing. of. large-scale. composites. structures.
are. presented. in. Automated VARTM Processing of Large-Scale Composite
Structures .(2004). 14 .Instead.of.using.the.lay-up.of.the.dry.reinforcing.ibers.in.
the.SCRIMP.or.VARTM.process,.it.may.be.more.proitable.to.use.automatic.
3-axial.braiding.
A.braider.in.Figure 2.11.(pos..3).moves.along.the.mandrel.on.the.rails.(pos..
5).and.iber.(pos..2).waving.on.the.mandrel.from.the.rollers.(pos..4).to.form.
a.wind.blade.(pos..1).
The.3-axial.braiding.process.is.inished.when.we.use.prepreg.and.roving.
iber..In.a.case.of.dry.ibers,.a.smart.molding.VARTM.process.is.used.to.open.
the.injection.gates..Opening.of.the.injection.gates.is.possible.when.the.area.is.

4 1 2

3

1. Wind blade
2. Fiber
3. Rollers
4. Rails

Braiding wind turbine blade automation process

FIGURE 2.11
Braiding.wind.turbine.blade.automation.process.